The invention relates to data storage apparatus and more particularly to rotatable magnetic disks. Still more particularly, the invention relates to controlling circuitry for moving a transducer into registration with a desired track on the magnetic disk.
Previously, several techniques have been used to provide the registration of a transducer on a magnetic track of a rotatable disk with high track densities. The two most common approaches have used dynamic servoing with a linear voice coil motor to access a transducer using either a separate servo head on dedicated servo tracks or using sector servoing in which the servo information is disposed in radially extending sectors interleaved with sectors of data. In either case, the servo information is derived and processed with an analog servo channel dedicated to this task, and such an approach is disclosed, for example, in John R. Taylor U.S. Pat. No. 3,936,876.